This invention is an apparatus for automatically following a curve lying substantially in a plane and for producing digital output signals indicative of the mathematical shape and/or location of the curve.
At the outset, it should be understood that the use of the word "curve" is intended to generically cover all lines whether straight or having a finite radius. A straight line, as is well understood, is simply a curve having a radius of infinity.
Prior art curve followers fall into one of two categories. The first are the followers using a single or double sensor to detect points on a line thereby inferring a direction and hence tracking a continuous line. There is no commercially available apparatus utilizing this technique known to the applicant which can be used for digitizing drawings in such a way that they can be readily retrieved and used by computer aided design software. The second category known to the applicant are those line followers that use array sensors and scan the drawing to produce and record digital (raster or pixel) image or picture of the object; which picture can then be analyzed by computer software, e.g., CAD, using image processing, and other techniques such as "edge enhancement" so as to identify geometric shapes and record the shapes in vector format. The resulting vectorizing image is a close approximation of the actual line drawing and consists of a collection of lines and arcs but no "intelligence" is associated with it; the user must then use CAD software to review the resulting picture and assign necessary intelligence to the drawing.